1. Field of the Invention
This invention relates to an improved process for the preparation of cumyl peroxides or cumyl diperoxides. More particularly, the invention relates to an improvement in the process of preparing cumyl peroxides by reacting an aliphatic or cycloaliphatic hydroperoxide or aliphatic dihydroperoxide, an olefin and a cumyl halide corresponding to the olefin under non aqueous conditions in the absence of a free acid and in the presence of a phenol catalyst.
2. Description of the Prior Art
The preparation of aralkyl and alkyl peroxides is well known in the prior art and can best be summarized under four major methods of preparation:
(1) The acid-catalyzed condensation of a hydroperoxide with an alcohol. PA1 (2) The acid-catalyzed addition of a hydroperoxide to an olefin. PA1 (3) The displacement reaction between an alkali metal salt of a hydroperoxide and an alkyl halide. PA1 (4) The displacement reaction between a hydroperoxide or hydrogen peroxide and an alkyl halide in the presence of an acid acceptor. PA1 where y is 1 or 2; PA1 when y is 1, R is selected from lower t-alkyl of 4 to 8 carbons, lower t-alkynyl of 5 to 8 carbons, t-aralkyl of 9 to 12 carbons or t-cycloalkyl of 6 to 10 carbons; and when y is 2, R is selected from ##STR3## where R.sup.1 is an alkyl of 1 to 6 carbons. Suitable hydroperoxides include t-butyl hydroperoxide, t-amyl hydroperoxide, t-hexyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, cymene hydroperoxide, p-menthane hydroperoxide, 1-methylcyclohexyl hydroperoxide, 1-methylcyclopentyl hydroperoxide, 3-hydroperoxy-3-methylbutyne-1,2-hydroperoxy-2-methyl-4-hydroxypentane and 1-hydroperoxycyclohexylacetylene. Suitable dihydroperoxides include 2,5-dimethyl-2,5-dihydroperoxyhexane, 2,7-dimethyl-2,7-dihydroperoxyoctane, 2,5-dimethyl-2,5-dihydroperoxyhexyne -3 and diisopropylbenzene dihydroperoxides.
The fourth method is the only method relevant to this invention. The other methods and their short-comings in the preparation of cumyl peroxide are thoroughly discussed in U.S. Pat. No. 4,133,835 (Bafford). This invention is essentially an improvement over Bafford's process as taught in U.S. Pat. No. 4,133,835. Prior art pertaining to the fourth method above is: Kato et. al. (Auslegeschrift No. 2,035,127) published a process for preparing t-cumyl type peroxides by reacting a tertiary hydroperoxide with an aralkyl halide, such as t-cumyl chloride, at 0.degree.-80.degree. C. in the presence of an acid binding agent such as a t-alcohol or an aliphatic olefin. The mole ratio of the aralkyl halide to the hydroperoxide could vary from 1:1 to 1:1.5. In this process the hydroperoxide reacts with the aralkyl halide to form the peroxide; the HCl generated is taken up by the acid binding agent. There is no regeneration of the t-cumyl chloride. Kato's process was run with an acid sensitive aralkyl hydroperoxide, cumene hydroperoxide, with t-cumyl chloride in the presence of t-butyl alcohol (see Example XX). Although the reaction ran quite fast, only a 36% yield of dicumyl peroxide was obtained. There was a considerable amount of phenol generated during the reaction indicating the t-butyl alcohol was not a good scavenger of the hydrogen chloride; consequently a large amount of the cumene hydroperoxide underwent acid catalyzed decomposition to form phenol and acetone.
Kloosterman et al. (Auslegeschrift No. 1,216,305) describes a process for the preparation of dicumyl peroxide and its ring chlorinated derivatives by the reaction of t-cumyl chloride or its ring chlorinated derivatives with an aqueous solution of hydrogen peroxide at 0.degree.-40.degree. C. in the presence of an acid binding medium so that the pH of the reaction mixture stays between -1 and 2.5 on a glass/Kalomel electrode. In a stronger acid medium, decomposition exotherms were reported to occur. A mole ratio of t-cumyl chloride to hydrogen peroxide of 1:0.5 to 1:0.8 were used in this system. The anhydrous basic acid binding agents, such as Na.sub.2 CO.sub.3, K.sub.2 CO.sub.3 or NH.sub.3, had to be added portionwise throughout the reaction so that the pH held between -1 and 2.5.
Bafford's (U.S. Pat. No. 4,133,835) process consisted of adding an aliphatic or cycloaliphatic hydroperoxide to an olefin such as a 1-aromatic-1-substituted ethylene and a halide corresponding to the ethylene under essentially anhydrous conditions in the absence of a free acid, at a temperature below the decomposition temperature of the halide. The main object of this invention was to provide a process for the preparation of certain peroxides, especially acid-sensitive peroxides by a procedure that does not use a free-acid catalyst. The process is similar to that of Kato's except Bafford uses the 1-aromatic-1-substituted ethylene as the acid binding agent. By doing this aralkyl halide is regenerated. Consquently, a low concentration of the aralkyl halide in the olefin can be used; the reaction becomes less acid sensitive and the economics are much better. Bafford stresses the importance of having an excess of hydroperoxide over the olefin/aralkyl halide.
None of the prior art teaches the use of phenols as catalysts; to the best of our knowledge there never has been any mention in the literature of using phenols as catalysts for making peroxides.